Producing gasolines



Patented Apr. 25, 1944 UNITED STATES PATENT OFFICE.

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No Drawing. Application March 27, 1941, Serial No. 385,465

12 Claims. (01.19am) stocks, for example, by cracking gas oils or otherheavy hydrocarbons or by transformation of light or heavy naphthas. Itis especially concerned with a catalytic process for improving thecharacteristics of such gasolines.

High compression spark ignition engines, for example, of the typeemployed in modern commercial and military aircraft, require fuelsmeeting exacting specifications, including high anti-knock rating andstability. In preparing such fuels, it has been necessary to buildsuitable base stocks up to anti-knock specifications by use of additionagents, for example, lead tetraethyl. With many acceptable base stocks,use of maximum permissible quantities of addition agent has not yieldedthe desired anti-knock rating. Consequently, it has been necessary toinclude in the base stock substantial quantities of expensive highanti-knock blending agents, for example, aikylation products orhydrogenated polymers, often in quantity exceeding the amount of lessexpensive portions of the base stock.

The base stocks themselves must meet exacting specifications. They musthave the stability required /of the finished product. They must alsohave reasonably high octane rating. In addition, they must be subject tosubstantial increase in anti-knock with use of permissible quantities ofaddition agent, i. e., they must have good response or susceptibility tosuch agents. Straight-run gasolines of proper end point have been themost commonly used base stocks. Because of the low are incapable ofmeeting stability specifications of aviation grade fuels. Many of themalso fail to have other properties which would make them suchdecomposition cts to the extent necessary to produce gasolin tion basestocks have failed to yield products capable of competing commerciallywith straightrun distillates on the basis of quality, that of price, orboth.

However, notable exceptions to the general class of gasolines are thoseproduced from selected charging stocks and with the aid of selectedcomposite catalysts obtained or derived from synthetic inorganic gelsand the like. Certain processes capable of producing base stocks whichsatisfy the high stability and other specifications of aviation basestock aredescribed in the following copending applications of John R.Bates: Serial No. 310,762, filed December 23, 1929; Serial No. 365,923,filed November 16, 1940; serial No. 365,924, filed November 16, 1940.The invention, however, is not concerned with treatment of straight-rungasolines to improve substantially their anti-knock ratings, or of othergasolines which, as produced, meet stability and other specificationsfor base stocks of the type hereinabove described.

One object is to produce stable aviation base stocks and other motorfuels from gasolines produced by decomposition and having unsatisfactorystability. Another object is to provide base stocks superior in qualityto straight-run distillates. Another object is to avoid depreciation ofanti-knock rating. Another object is to improve susceptibility toaddition agents. Another object is to minimize or even to eliminate theuse of high anti-knock blending agents in producing aviation gasolinesof commercial and fighting grades. Other objects will be apparent fromthe detailed description that follows.

The invention involves subjecting gasolines of low stability produced bydecomposition reactions to the action of silicious splitting catalystsat cracking conditions controlled to efiect' appreciable production 01gas and coke without afiecting substantially the anti-knock of the,gasoline charge. The surprising and unexpected discovery has been madethat gasolines of low stability produced, for example, by cracking orreforming.

reactions, when subjected to cracking in the presence of silicioussplitting catalysts are improved in stability to an extent that isdependent upon suitable for such use. Many attempts to refine o theextent of crackins as measured y the proof the duality of aviaduction ofgas, coke, or both. By splitting catalysts, reference is made tocatalysts which promote decomposition of hydrocarbons predoml nantly byrupture of carbon-to-carbon linkages in contradistinction todehydrogenation catalysts which act predominantly to increaseunsaturation by rupture of carbon-to-hydrogen linkages. In practice ofthe invention, substantial improvement of stability is ordinarilyobtained only when the cracking conditions are sufllciently severe toconvert at least 1% by weight of the charge into coke.

It is preferred that the charge be free or substantially so ofcomponents above the gasoline boiling range, above about 440 F., becausehigher boiling hydrocarbons often are subject to complex decompositionprocesses including those which produce unstable lower boilingmaterials. However, when the desired stable product is a low boilingdistillate, for example, aviation gasoline of 275 to 350 F. end point,higher yields of such products are obtained when the gasoline chargeproduced by decomposition reactions contains or has added to it anaphtha, preferably produced by decomposition, which is higher boilingthan the desired product.

Coke produced accumulates on the catalyst as deposit. The stability ofthe cracked gasoline falls off substantially when the total quantity ofcharge fed is such that the accumulated deposit exceeds a lowproportionate quantity of the catalyst, usually 50 grams per liter ofcatalyst. It is preferred to avoid deposits in excess of this amount.For best results, especially when the desired product is aviation basestock, it is preferred to limit the total accumulated deposit til 25 oreven grams per liter of catal st.

When the selected quanti y of deposit is reached, the feed to thecatalyst is cut oil. The catalyst may then be rejected but preferably isregenerated by combustion at controlled temperature, preferably not inexcess of about 1100 F. In commercial practice such regeneration isordinarily effected at frequent intervals, usually after runs notexceeding a few hours, say 4 to 8 hours, in length, and often after runsof an hour or less, for example, of 10 to 30 minutes duration. Thus, toprovide continuous flow through the plant, a plurality of converters ofsuitable design adapted for use alternately onstream and in regenerationmay be employed, the flow being transferred from one converter toanother at desired intervals so that there is always at least oneconverter on-stream while one or more is being subjected toregeneration.

Porous adsorptive contact masses which promote cracking of hydrocarbonshigher boiling than gasoline into substantial yields of stable gasolineare employed as catalysts. Satisfactory catalysts include active oractivated plural component silicious materials having substantialcracking activity, for example, blends of silica and alumina of suitableactivity obtained from natural or synthetic sources.

Because of the wide variation in results that are obtainable fromdifferent higher boiling hydrocarbon charging stocks and from differentcombinations of reaction conditions, cracking activity of a catalyst, asreferred to herein and inthe appended claims, is the per cent gasolineobtained by utilization of the catalyst with a selected charging stockunder definite cracking conditions. A refractory paraiiinic virgin gasoil having substantially the following properties is utilized as theaforesaid selected charging stock.

A. P. I 36.0:03"

Engler distillation, F.:

Int 440 5%- 464 10% 484 20% 498 30% '510 40% 522 50% 534 60% 550 572 600-1 646 704 Dry point (96-99%) 724 Sulphur, per cent wt 0.3

Pour, "F 35:5 Flash, F. open cup 220:10 Fire, F 2501-5 S. U. via/100 F40:3 Conradson carbon 0.03 Aniline point, F.. 16512.5

Several degrees variation in the distillation temperatures throughoutthe range of the abo've Engler are permissible without any substantialeffect upon the yield of gasoline. Gas oils having the requisiteproperties may be obtained as straight run distillates from East Texascrude or by blending other suitable parafllnic distillates in knownmanner. For the purposes of this invention, the activity of the catalystis the per cent. by liquid volume, based on the charge, of 410 F. endpoint distillate separated from synthetic crude condensed at 60 F. andobtained by passing the vaporized gas oil for a period of 10 minutes atsubstantially atmospheric pressure and at rate of one and one-halfvolumes per hour (liquid basis) over one volume of catalyst maintainedat 800 F.

In practice of the invention, catalysts of at least 15% activity asabove defined should be employed. Better results are obtained with andit is preferred to utilize catalysts of at least 20% activity, forexample, those within or above the range of 25 to 40% activity.

Preferred silica-alumina catalysts are blends of silica and alumina inthe weight ratio of 3%:1, 4:1 or higher, prepared synthetically orderived from naturally occurring earths. Of particular value are suchblends which are free or substantially so of the alkali metals, sodiumand potassium. These catalysts not only have the requisite activity butalso maintain desired activity for long periods of use involvingfrequent and repeated regenerations. One method of preparing active andstable synthetic silica-alumina blends is by interreaction of solutionsof soluble silicate and of a soluble aluminum compound under controlledpH of 11 or below to produce a zeolitic gel and then to remove thedesired amount of alkali metal by base exchange with a solution of avolatile or unstable cation such as ammonium,

with most cracked gasolines, the desired high ly stable product isobtained with temperatures in the range of 100 to 900 F. with apreferred range of 750 to 875 F. Temperatures above about 900 F. tend tocause thermal decompositions which form unstable products and should beavoided. In selecting temperatures within the above ranges, it is bestto consider other operating conditions, especially specific catalystactivity. With higher catalyst activity lower temperatures will producefrom a given gasoline charge the yield of coke and gas necessary for thedc:- sired extent of refining. Temperatures above that which yields onlythe necessary quantity of these by-products eil'ects still furtherimprovement in quality of the gasoline, if further improvement ispossible, but often at the expense of increased proportionate quantityof coke, gas, or both. Consequently, in the interest of higher yields,it is preferred to employ temperatures which, although high enough topromote cracking to the desired extent, are of such order as to avoidsubstantial excess of either or both these by-products. Naturally, theparticular temperature or range of temperatures best suited for aparticular gasoline charge will vary with the ease with which thatgasoline can be cracked. Generally, with catalysts of about 25% activityor greater, the desired amount of cracking is obtained at temperature ofat least 700 F. but not in excess of 850 F., as within the range of 750to 840 F. with most gasolines obtained by decomposition reactions.

The conditions of rate and pressure are selected to give contact timesin the catalyst chamber sufficiently high to effect cracking of thegasoline charge and sufliciently low to prevent substantial change inoctane. Contact times employed are usually at least 15 seconds, based onthe volume of the catalyst chamber, and may be as high as 250 seconds asfor example, from 20 to 250 seconds. The general trend is for highercontact times within the above range the greater the improvement instability that is to be effected. with catalysts of at least 20%activity and especially with those of at least 25% activity, many if notmost unstable gasolines are converted into products having the highstability necessary for aviation fuels with contact times of 100 secondsor less.

Desired contact time may be obtained simply by regulation of feed rateat substantially atmospheric pressure. However, use of superatmosphericpressure accelerates the desired improvements in the characteristics ofthe cracked gasoline charge and, in addition, permits use of higher feedrates. Accordingly, it is preferred to utilize superatmosphericpressure, for example, at least 25 lbs. per square inch gauge. Excessivepressures, however, tend to produce excessive coke and gas losses. Withmost cracked gasolines, pressures within the range of 50 to 200 lbs. persquare inch gauge may be employed without incurring excessive gas andcoke losses. It is preferable to avoid pressures substantially aboveabout 200 lbs. because at higher pressures the proportionate quantitiesof these by-products in crease rapidly.

With pressures of 25 lbs. per square inch or greater, the requisiteamount of reaction is usually obtained with feed rates of at least 3volumes of liquid charge per hour to '7 volumes of catalyst. Pressureswithin the range of the order of 50 to 200 lbs. per square inch gaugeordinarily may be accompanied with feed rates of at least one volume ofcharge per hour per volume of catalyst,

as for example, within or above to 8 volumes.

Several tests or combination of tests may be utilized as the measure ofstability. Exemplary tests include ongen bomb induction periods (A. S.T. M. test D525-40T), Army-Navy accelerated gum determinations (TestF-5d described in U. 8. Government pamphlet AN-VV-F-776) and acid heat(A. S. T. M. test D481-39). Acid heat (equivalents are bromine numberdeterminations such as those utilized by the French and ItalianGovernments) has been utilized for the purposes of this invention as aconvenient test. This test. although it does not measure stabilitydirectly, is actually indicative of stability because it is a measure ofthe quantity of unsaturated and usually olefinic components in thegasoline which are'susceptible to or capable of oxidation to produceundesired gum and color forming bodies. One. convenient measure of theextent of cracking is the per cent of charge that is converted to poke.Coke deposit and desired reduction in acid heat may be correlated toserve as a basis for selecting suitable cracking conditions. Thus, intreating unstable gasolines of aviation boiling range, to produce basestocks for commercial, training, or fighting grades of aviation fuel, itis desired to obtain products having acid heats within or below therange of 60 F. to 15 F. and preferably not in excess of about 40 F. ToProduce such stocks from typical but comparatively stable cracked chargehaving acid heats 40 to 60 F. higher than that desired, coke equivalentthe range of 1 to about 1% by weight of the charge should be produced,typical operations yielding up to about 3% by weight of coke. With lessstable charging stocks, for example, those whose acid heats are to F.higher than desired, it is ordinarily necessary to obtain coke depositsof at least 2% by weight, as for example, from 2% to 5%. When thedesired acid heat reduction is about F. or more, the coke productionusually must be about 3.5% or more, for example, 3.5% to 10%. The cokeyield necessary to provide determined reduction of acid heat will varysomewhat with the basic chemical composition of the cracked or otherdecomposition-produced gasoline charged, as governed by the conditionsand method employed in its production. Thus, with somedecomposition-produced gasolines, for example, highly refractory crackedproducts, it is desirable to utilize cracking conditions which producelarger quantities of coke than indicated by the lower values of theabove ranges. Also. greater quantities of coke are sometimes producedwhen the charge is a wider boiling range fraction than the desiredproduct, as for example, when the charge is a gasoline of 420 to 440 F.end point and the desired product is of lower end point, for example,aviation gasoline.

Gas produced during the operation may be similarly correlated withstability improvement desired. Ordinarily, the per cent by weight ofcharge converted to gas will range from about at least 0.5 for acid heatreductions of about 40 to 60 F., to about 10 for acid heat reductions of200 'F. or more. In most instances, however, coke production provides abetter basis for selecting reaction conditions because the quantity ofgas is often more subject to substantial variation with minor changes inone or more reaction con- 7 ditions, and especially of temperature.

It is to be understood that the invention is not limited to use ofcracking conditions which produce minimum or optimum quantities ofbyproducts considering the improvement in quantity of gasoline chargethat is desired. On the contrary, the highly stable products resultingfrom practice of the invention are obtained under more severeconditions. ,So long as the conditions of cracking are at least severeenough to provide at least the quantities of cracked by-productsnecessary to effect the desired degree of improvement in the gasolinecharge, highly stable and otherwise improved products are obtained.

As an incident to the cracking reactions, a small portion of thecharging stock is usually converted into higher. boiling hydrocarbons ofthe nature gas oil. These are separated in suitablemanner from thegasoline produced, as by fractionation. Also, if the charge containsorganic sulphur compounds, these are decomposed to produce hydrogensulphide which, in order to yield a finished non-corrosive product,may-be removed by any suitable method, as for example, by fractionationtalned at about the same temperature under pressure of the order of200lbs. per sq. in. gauge and 0.01%, its navy gum about 0.5 milligram,and its color 30. A. P.'I. Under the operating conditions here employed,the contact time was about 96 seconds; The catalytic cracking reactionproduced, in addition to the liquid products, about 8.4% by weight ofcoke and oi. the order of 3.7% by weight of gas. The quantity of cokeaccumulated on the catalyst was found to be about 10.5 grams per liter.When the same distillate was subiected to another batch of the abovecatalyst (after regenerasuch as utilized in removing excess lightordinarily v gaseous materials from ,the condensed gasoline to provide afinal product of desired vapor pressure. Another method of removingsulphurous material from the products of the catalysis is to contactsuch products 'preferaly in vapor form and at reduced temperature, forexample, within the range of 400 to 650 F. with contact materialcontaining a metal or metal oxide capable of reacting with sulphurbearing components of the vapors to absorb sulphur. Such contact massesmay comprise, for example, nickel, cobalt or copper in oxide formdeposited or otherwise incorporated in an active or inactive poroussupport, preferably silicious, and comprising for example silica andalumina. Suitable active supports include active blends of silica andalumina suitable for use as catalysts for the preceding cracking step.

Although production of base stocks for aviation gasolines is animportant application of the invention, it is by no means the. onlyapplication. On the contrary, the invention finds application in theproduction of any desired highly stable hydrocarbon fraction which boilswithin the boiling range of gasoline or the like. Another specificapplication is in the production of high quality gasolines of the typewhich commands premium prices on the motor fuel market. For example,

' cracked motor gasoline, which is unsuited for use Example 1 A crackeddistillate of aviation boiling range having an acid heat of about 132F., octane rating of about 79 (CFR-MM) which could be raised toapproximately 86 by the addition of 3 cc. per gallon of tetraethyl lead,navy gum of 377 milligrams, A. P. 1. color of 13, and sulphur content of0.035% by weight, was contacted with an activated hydrosilicate ofalumina of about 28% activity composed to the extent of at least 90% byweight of silica and alumina in the weight ratio of' about 4:1. Thedistillate, after preheating to about 820 E, was fed to thesilica-alumina catalyst mintion of the latter by controlled combustion)for a 20 minute run period in which temperature of about 820 F., feedrate of about 2:1, and pressure of about 100 lbs. were employed to givea contact time of the order of 33 seconds, the fractionated products ofaviation boiling range had acid heat of about 39 F., navy gum of theorder of 11 milligrams, sulphur content of about 0.02%, and cotanerating of about 79 which could be raised to approximately 89 with 3 cc.of tetraethyl lead per gallon. In this operation, the production of gasand coke was about 2.6% and 2.0% respectively and the coke accumulatedon the catalyst was of the order of 10 grams per liter.

Example 2 lyst of about 34% activity and similar in composition to thatemployed in Example 1, at temperature of about 840 F., feed rate ofabout 1:2, and pressure of the order of 50 lbs. per sq. in. for anoperating period of 20 minutes duration. The cracking reaction producedof the order of 8.6% by weight of coke, 8.3% by weight of gas, and aliquid product which upon fractionation yielded a fraction of aviationgasoline boiling range having acid heat of about 20 F. and octane ratingof the order of which could be raised to .above 90 by the addition of 8cc. of tetraethyl lead per gallon, and was otherwise suitable for use asa base stock in the production of commercial or fighting grades ofaviation fuel. The reaction conditions employed in this run gave contacttime of the order of 75 seconds. Accumulated coke deposit wasapproximately 10 grams per liter of catalyst.

When another batch of the same charging stock was contacted with thesame catalyst in regenerated condition under modified conditions of rateandpressure (rate of 0.75:1 and pressure of 200 lbs. per sq. in.) togive a contact time of the order of seconds for another 20 minute run,an aviation base stock having an acid heat of only 12 F. was producedtogether with about 10% by weight each of gas and coke, the coke depositthen amounting to about 18.5 grams per liter of catalyst.

, small quantities in conjunction with silica and alumina, eitherdeposited on or otherwise uni-- Ezample 3 A gasoline of aviation boilingrange produced by fractionation of a cracked motor iuel of about 390 F.end point and having octane rating of about 79 which could be raised toapproximately 90 by the addition of 6 cc. of tetraethyl lead and havingan acid heat of about 147 F. when contacted with catalyst similar tothat employed in Example 1, at temperature of about 820 F., feed rate ofabout 0.9 to 1, and pressure of the order of 50 lbs. per sq. in. (theseconditions giving contact time of about 42 seconds) yielded about 81% byvolume of an aviation gasoline boiling range distillate of about 45 F.acid heat, whose octane of about 79 could be raised to 95 by theaddition of 6 cc. per gallon of tetraethyl lead and to above 91 withonly half this quantity of addition agent, together with about 3.0% and5.8% by weight, respectively, of coke and gas. When the entire motorfuel, which contained approximately 20% by volume of components heavierthan aviation gasoline, was contacted with the freshly regeneratedcatalyst under the same operating conditions except a slightly increasedrate of about 1:1 (giving contact time of about 38 seconds),fractionation of the liquid products produced aviation gasolinedistillate of about 40 F. acid heat and octane rating of about 79 whichwas raised to about 94.5 by the addition of 6 cc. of tetraethyl lead.This distillate amounted to somewhat more than 89% by volume of theaviation gasoline content of the charge. The coke and gas produced wereabout 2.6 and 3.4% by weight, respectively. In both the above runs, theaccumulated catalyst deposit was approximately 6.5 grams per liter ofcatalyst.

Example 4 A cracked aviation gasoline having acid heat of about 114 F.and octane rating of the order of 78 (AFB-1C method), which could beraised to about 90 by the addition of 4 cc. of tetraethyl lead, wasconverted into an aviation base stock having acid heat of about 17 F.and octane rating of about 78, which was raised to about 90 with only 3cc. of tetraethyl lead per gallon and to 93 upon addition of one morecc. of this material. To effect the conversion, the aviation gasolinecharge at temperature of about 790 F., feed rate of the order of 1.5:1and pressure of about 50 lbs. per sq. in., and an operating period of 10minutes, was subjected to the action of a catalyst of about 31% activitycomposed substantially entirely of silica and alumina and Produced bycoprecipitation of these materials from a soluble silicate solution andsodium aluminate solution in the presence of ammonium sulphate to form azeolite from which substantially all alkali metal was removed by baseexchange with ammonium chloride solution and by calcination of theresulting purified zeolite. The contact time was about 26 seconds. Thecoke produced in this operation was about 2.5% by weight of the chargeand the gas about 3.1% by weight. The accumulated coke deposit wasapproximately 4.7 grams per liter of catalyst.

It is to be understood that theinvention is not .formlyincorporated in asuitable synthetic silicaalumina blend or activated hydrosilicate ofalumina, or it may replace, in whole or in part,

the alumina content 01' a silica-alumina catalyst.

Suitable diluting agents, for example, steam, may be fed to the catalysttogether with the gasoline charge to provide, as desired or necessary,additional control over time of contact. In some instances. smallamounts of steam so used may also contribute to the improvement instability characteristics.

I claim as my invention:

1. In refining fuel of the gasoline type the steps of subjectinggasoline produced by decomposition reactions in the presence of anadsorptive silicious splitting catalyst of at least 20% activity tocracking conditions including temperature within the range of 700 to 900F. regulated to effect cracking of at least 1% or said charge into cokebut only sufllcient to reduce acid heat with-* out aflectingsubstantially the anti-knock of the charge, and limiting the quantity ofcharge fed to said catalyst to produce coky deposit thereon not inexcess of 50 grams per liter thereof.

2. The process of reducing the acid heat of gasolines produced bydecomposition reactions comprising the steps of subjecting suchgasolines in the presence of an active silicious cracking catalyst of atleast 20% activity to cracking conditions including temperature above750 F. insufllcient to effect substantial thermal decomposition of saidgasoline, regulating said cracking conditions to effect decomposition ofat least 1% by weight of said charge into coke but only surficient toreduce acid heat without substantial change in octane rating of saidcharge, limiting the quantity of gasoline fed to the catalyst to producecoky deposit thereon not in excess of 50 grams per liter thereof, andseparating from the products a gasoline having substantially the octanerating or said charge.

3. The process of refining gasolines produced by cracking, reforming, orthe like comprising the steps oi. subjecting such gasoline in vaporphase and absence of higher boiling hydrocarbons to cracking attemperatures of at least 750 F. insuiilciently high to effectsubstantial thermal cracking in the presence of a silicious crackingcatalyst of at least 15% activity, regulating said cracking conditionsto convert atleast 1% by weight of said charge into coky deposit butonly sufilcient to reduce acid heat, limiting the quantity of gasolinefed to said catalyst to produce deposit not in excess of 25 grams perliter of catalyst, and separating hydrocarbons boiling outside thegasoline boiling range from the products of the aforesaid catalysis.

4. The process of improving oxygen stability and other characteristicsof gasolines of high octane rating produced by decomposition reaclimitedto the use of silica and alumina catalysts tions comprising the step ofsubjecting such gasoline substantially free of higher boilinghydrocarbons to transformation in the presence of a silicious catalystof at least 20% activity for promoting transformation of hydrocarbonshigher boiling than gasoline into substantial yields of gasoline undersuch controlled conditions, including cracking temperature of at least750 F., insufiicient to eflect substantial thermal crackin of saidgasoline, and contact time of at least 15 seconds, that at least 1% byweight of the gasoline charge is decomposed to coky deposit to reduceacid heat without substantially affecting the anti-knock rating of saidcharge, and renewing or regenerating the catalyst before the coky de--posit thereon reaches 50 grams per liter.

5. In the production of fuels or the gasoline type stable to oxidation,the process oi contacting a gasoline produced by decomposition processeswith a silica-alumina cracking catalyst of at least 20% activity undercracking conditions including temperature withinthe range of 100 to 900F. and contact time in the range of 15 to 250 seconds, limiting saidcracking conditions to con- .vert at least 1% by weight oi said gasolineinto coke, restricting the quantity of gasoline charge contacted withthe catalyst to limit the quantity of colw deposit accumulated on thesame to not in excess of 25 grams per liter thereof, and separating afraction of gasoline boiling range from the resulting products. 1

6. In reducing acid heat of fuels oi the gasoline type, the process ofcontacting a gasoline produced by cracking, reforming or the like, andhaving acid heat in excess of 60 F., under cracking conditions includingtemperature within the range of 700 to 900 F. for 15 to 100 seconds witha silicious splitting catalyst of at least 20% activity, regulating saidcracking conditions to effect decomposition oi suillcient quantity ofsaid charge, at least 1% by weight, into coke to reduce the acid heat ofthe charge at least 40 F., separating a fractionof gasoline boilingrange from the resulting products, and limiting the quantity of chargecontacted with the catalyst to restrict the coke depomt accumulated onthe latter to 25 grams or less per liter thereof.

'7. The process of converting gasolines to reduce their acid heatcomprising the steps of subjecting a gasoline produced by decompositionhaving acid heat of at least 60 F. to the action of a silica-aluminacracking catalyst of at least 25% activity under vapor phase crackingconditions including temperature within the range of 750 to 875F.,-superatmospherlc pressure below about 200 lbs. per sq. in., andcontact time within the range of 20 to 250 seconds, controlling saidcracking conditions within the above ranges to effect suillcientdecomposition of said charge, at least 1% by weight, into coke to reduceby at least 40 F. the acid heat of that portion of the charge boilingwithin the boiling range of aviation gasoline, limiting the totalquantity of charge contacted with said catalyst during a run to restrictthe accumulated coky catalyst deposit to less than 50 grams perliter ofcatalyst, and separating a gasoline fraction of reduced acid heat fromthe reaction products.

8. The process ofproducing aviation ba'se stocks from gasolinescomprising contacting a gasoline of motor fuel boiling range produced bydecomposition reactions and having acid heat in excess of 60 F. with asilicious splitting catalyst of at least 15% activity under crackingconditions including temperature within the range of 700 to 900 F.superatmospheric pressure of at least 25 lbs. per sq. in. and contacttime of at least 15 seconds, controlling said cracking conditions toincrease the quantity of components within the boiling range of aviationgasoline and to effect suillcient decomposition of said components, atleast 1% weight thereof, into coke to eifect reduction of at least 40 F.in the acid heat thereof, restricting the quantity of motor gasolinecontacted with assure said catalyst to limit the coky deposit to notmore than 25 grams per liter of catalyst, and

separating a fraction-of aviation gasoline boilins range from theresulting reaction products.

9. The process of producing motor fuel oi improved resistance tooxidation from sulphur bearing gasoline containing unstable unsaturatedlaydrocarbons produced by decomposition reactions comprising subjectingsaid gasoline to the action of a silicious splitting catalyst of atleast 20% activity under cracking conditions including temperature above750 F. but below thermal decomposition temperature controlled to effectdecomposition into coke of at least 1% by weight of said gasolinewithout affecting substantially its anti-knock rating, removing sulphurbearing components from the products of the cracking step, andregenerating the catalyst before the coky deposit thereon reaches 50grams per liter.

10. The process of improving resistance to oxidation of high anti-knockgasoline produced .-.by decomposition comprising subjecting suchgasoline to the action of a catalyst of at least 25% activity forpromoting cracking of hydrocarbons heavier than gasoline intosubstantial yields of gasoline under such cracking conditions includingtemperature in the range of 750 F. to 875 F. and contact time in therange of 15 to seconds that at least 1% by weight of the charge isdecomposed to coky deposit without aflecting substantially theanti-knock rating of the charge, and limiting the quantity of the lattercontacting with the catalyst during a run to produce cow deposit not inexcess of 25 grams per liter of catalyst. v

11. The process of refining gasolines produced by cracking, reforming orthe like comprising subjecting such gasoline substantially free ofhigher boiling hydrocarbons to the action of a splitting catalyst fortransforming hydrocarbons heavier than gasoline into gasoline and havingat least 25% cracking activity, maintained at cracking conditionsincluding temperature of at least 750 F. but insufllcient to effectsubstantial thermal decomposition of said gasoline, regulating saidcracking conditions to establish a contact time of at least 15 secondsunder superatmospheric pressure of at least 20 lbs. per square inch soas to effect decomposition of at least 1% by weight of said charge intocoke, separating from the products a gasoline fraction of approximatelythe octane rating of said charge, and renewing or regenerating saidcatalyst before the coky deposit thereon exceeds 50 grams per liter.

12. The process of producing stocks for aviation gasoline from motorgasolines produced by decomposition comprising subjecting such gasolinesubstantially free of higher boiling hydrocarbons to cracking conditionsin the presence of a splitting catalyst of at least 25% crackingactivity under cracking conditions including temperature within therange of 750 to 875 F., superatmospheric pressure of at least 25 poundsper square inch, and contact time of at least 20 seconds, controlled todecompose at least 1% by weight of the gasoline charge into cokydeposit, separating a fraction of aviation gasoline boiling range fromthe converted product, and renewing or regenerating said catalyst beforethe coky deposit thereon exceeds 25 grams per liter.

ALBERT G. PETERKIN.

